On Dec. 7, 1971, two patents issued to one of the co-inventors hereof, Leo Esaki, such patents being U.S. Pat. Nos. 3,626,257 and 3,626,328 entitled "Semiconductor Device with Superlattice Region" and "Semiconductor Bulk Oscillator", respectively, both of which are incorporated herein by reference. These patents teach how to produce semiconductor devices with superlattice regions, the electrical properties thereof, and point out the prior state of the art with respect to theoretical considerations involving wave propagation in periodic structures, and the bulk negative resistance devices resulting therefrom.
Prior to our invention, Leo Esaki and Raphael Tsu, realized that the normal conduction band energy levels of a superlattice region are modified to produce supplemental allowed levels separated by infrared frequencies in superlattice structures. They taught that such devices could be useful as sources of infrared radiation and as laser amplifiers and oscillators.
It has long been known that GaAs and other alloys of Group III and Group V materials can be employed to emit light either as light emitting diodes or injection lasers. The emission of light in these devices is controlled by the current passed therethrough.